A traditional over-current protection method is merely able to configure a fixed over-current protection threshold by voltage-division of an external resistance, and said protection threshold usually is not in a position to take account of current protection values of a power module and a motor of an inverter simultaneously. For instance, where an over-current protection threshold configured by the inverter is the current protection value of the power module of the inverter, and the current protection value of the power module is greater than the current protection value of the motor, over-current protection of the motor is a mere software protection; where the over-current protection threshold configured by the inverter is the current protection of the motor, and the current protection value of the power module is greater than the current protection value of the motor, the over-current protection value of the motor is not able to be dynamically changed by software. In addition, where other motors with equal powers are used instead, due to discrepancy in current protection values of the motors, it is required to adjust an inverter hardware circuit to change the over-current protection threshold.